2000 discovery two. Replaced thermostat..cleaned out everything...fixed leak at throttle body heater plate..etc...have pumped up and put pressure on it and did that test. You can run for three minutes and it over heats. Dont seem to be head gaskets. My mechanic says it's definately not that. Thye water wont circulate. IS it the water pump? What do you think?
Thanks in Advance.
Steve

 

You're not losing coolant? You have pressure tested the motor and it is okay? If you answer yes to both of those it's probably not the head gaskets.

How many miles are on your truck and has the water pump ever been replaced? How do you know you're not circulating coolant? If you are not circulating coolant then I would think the water pump is the logical next step. You could have a cracked block -- or at least you WILL if you don't stop overheating the motor. When you say your truck overheats, does it boil over or do you just notice the temp rising? If the water pump is okay you need to administer a chemical test to see if combustion gases are escaping into your coolant.

 

114000 miles and bought it used. It appeas that the pump has never been replaced. There is not one coolant leak. He pumped it up and did the pressure test and rulled out the head gaskets, He's the one that says the water and antifreeze is not circulating. He also says the blockis not cracked due to his knowledge. I ordered a water pump. It's under a hundred dollars so it will be here tomorrow and we shall see.
Thanks for your input.

 

Check if the heater core is clogged.